Amalia Sholehah

Optimizing the Nanostructural Characteristics of Chemical Bath Deposition Derived ZnO Nanorods by Post-Hydrothermal Treatments

Zinc oxide (ZnO) is an inorganic semiconductor material which has been widely studied due to its various potential applications. Over the past decades, one-dimensional (1-D) nanostructures such as nanowires and nanorods have stimulated significant scientific interests because of their unique properties in comparison to bulk materials. For the application of dye sensitized solar cell (DSSC), 1-D ZnO nanostructures are more desired than the spherical nanoparticles since the former provides ballistic effect leading to faster electron transfer which in turn can increase the device performance. Motivated by this consideration, in the current study ZnO nanorods were deposited on ITO glass substrate via chemical bath deposition (CBD) process where the seeding solution was prepared at 0°C. In order to increase their crystallinity and optical properties, the as-deposited ZnO nanorods were subjected to post-hydrothermal treatment at 150°C for 3, 6 and 9 hours. The scanning electron microscope (SEM) analysis revealed that the ZnO nanorods were successfully grown as vertically-aligned hexagonal structure, while the X-ray diffraction (XRD) study showed that the intensity of (002) crystal plane is the highest peak for all nanorod samples. The optical study by UV-Vis spectroscopy showed that the absorption edge of the as-deposited sample was slightly red-shifted to visible region after post-hydrothermal treatment. The ZnO nanorods sample derived from post-hydrothermal treatment for 6 hours provided the optimum nanostructural characteristics with an average diameter of 228 nm, crystallite size of 27.97 nm and the band gap energy, Eg, of 3.12 eV.

High Coverage ZnO Nanorods on ITO Substrates via Modified Chemical Bath Deposition (CBD) Method at Low Temperature

In the present work, ZnO nanorods array were successfully grown on ITO substrate via chemical bath deposition method (CBD). The seeding solution was prepared at low temperature (0°C) using zinc nitrate tetrahydrate and hexamethylenetetramine. The as-deposited ZnO nanorods were hexagonal wurtzite structure growing vertically on the substrate. Various reaction times from 3 to 5 hours were applied upon the CBD process at 90°C. The results showed that the duration of reaction time has affected the nanorods array properties. With the increase of reaction time from 3 to 5 hours has increased the diameter and crystallite size of nanorods from 325 to 583 nm, and from 22.68 to 34.28 nm. As a result, the band gap energy, Eg of ZnO nanorods decreased from 3.63 to 3.13 eV.

The Effect of Precursor Mixing Temperature during Precipitation Process on the Size of ZnO Nanoparticles and the Dispersion of ZnO@SiO2 Core-Shell Nanostructure

ZnO nanoparticles have been used for many applications, including in cell labeling application. Its light emission can be used to determine and identify biology cells. Wet chemical precipitation method has been successfully done to synthesize the nanoparticle and it was subsequently continued by encapsulating with silica to keep ZnO stabilized in water to be properly used in cell labeling application. Varying precipitation temperatures has been performed to control the nanoparticle size and the addition of F127 surface active agent was carried out to prevent the agglomeration. The results showed the smallest nanoparticle (3.49 nm) was obtained from the process with temperature of 25oC, with the highest band gap energy, 3.12 eV. On the other hand, the largest nanoparticle (13.16 nm) was obtained from synthesis at temperature of 65oC, with the lowest band gap energy, 3.08 eV. These levels of band gap energy are potentially suitable for cell labeling application.

The Effect of pH and Heat Treatment on the Porous TiO2 Nanostructures Derived from Triblock Copolymer Templating-Precipitation Technique of TiOSO4 Solution

The synthesis and characterization of TiO2 nanostructure has become intensive nowadays because of its superior properties among other semiconductor materials. In this work, TiO2 nanostructures have been derived from ilmenite mineral by using precipitation technique with various pH and calcination temperature. The resulting nanostructures were characterized to investigate the effects of those variables on the phase, crystallite size, and band gap energy. The characterization was performed by using XRD, FT-IR, UV-Vis DRS, SEM, EDS, and TEM. The results showed that TiO2 sample prepared under low pH value of 0.3 demonstrated porous structures although they are not well-ordered yet, while the sample with a pH adjustment up to 7.0 provided nanotube structure. The biggest crystallite size of 3.43 nm and low band gap energy of 3.07 eV was obtained in the TiO2 samples synthesized without pH adjustment and calcined at a a temperature of 300°C. This characteristics shows that TiO2 nanostructure in this study is potential for the applications of dye sensitized solar cell (DSSC) and photocatalysist.

Controlling the Size and Dispersion of ZnO@SiO2 Core-Shell Nanostructure by Addition of Triblock Copolymer Surfactant and pH Adjustment during Precipitation and Encapsulation Process

The potential use of ZnO nanoparticles for cell labeling application has been improved over past several years. Focusing to overcome the tendency of the nanoparticles to aggregation, in this work ZnO nanoparticles have been synthesized by using surfactant-assisted precipitation method. The samples were then characterized by using XRD and UV-Vis Spectroscope. The results showed that the presence of surfactant could help controlling the crystallite size to become smaller (4.02 nm) as compared to the conventional precipitation method (9.45 nm). ZnO nanoparticles that had been coated by the surfactant was then re-coated again by silica shell to form ZnO@SiO2 core-shell. The presence of F-127 coating on the surface of the nanoparticles made the dispersion and the stability of crystallite size better in various encapsulation pH value (4.04 4.32 nm). The band gap energy of the ZnO nanoparticles (3.145 3.085 eV) also showed a good correlation with the crystallite size (4.02 10.38 nm). Therefore, the resulting ZnO@SiO2 core-shell in the present work are potential to be used in cell labeling application.

The Preparation of Porous TiO2 Nanostructure by Triblock Copolymers Co-Templating Method of TiOSO4 Solution Derived from Ilmenite Ore

Porous titanium dioxide (TiO2) nanostructure has been successfully synthesized by a modified solgel method using non-ionic triblock copolymer pluronic F-127 as surfactant template and titanylsulfate (TiOSO4) solution as the inorganic precursor derived from the sulfuric process of Bangka-Indonesia ilmenite ore. The resulting nanostructure samples were characterized by XRD, SEM, TEM and UV-Vis spectroscopy. The results showed that porous titania particles have sphere-like shape and can be indexed as the anatase phase with average crystallite size of about 5-7 nm, narrow pore size distribution with an averange pore diameter of about 3-5 nm and band gap energy in the range of 3.10 3.16 eV.

Controlling the Crystallite Size of Zinc Oxide Nanorods via Chemical Bath Deposition and Post-Hydrothermal Treatment

ZnO nanorods were deposited on ITO glass substrate via chemical bath deposition at low temperature of 90°C. The seeding solution was made by dissolving zinc nitrate tetrahydrate and methenamine in cool water (5°C). The as-synthesized ZnOs were further subjected to post-hydrothermal treatment series.The results of scanning electron microscope (SEM) studies showed that the ZnO nanorods were grown as vertically-aligned hexagonal structure, while x-ray diffraction (XRD) patterns showed a high intensity of [002] peak. The absorption spectra of the as-synthesized sample indicated a strong absorption peak near the UV region. After post-hydrothermal treatments, the absorption was slightly shifted to visible region. The ZnO nanorods sample derived from post-hydrothermal treatment at 150°C for 12 hours has the largest crystallite size of 269.402 nm and the lowest band gap energy, Eg value of 3.205 eV.

Synthesis and Characterization of Zinc Oxide Tetrapods from Zinc Galvanization Dross

As an interesting material in large field area, ZnO synthesize has been widely observed. In this research, synthesize was carried out using zinc dross, waste from galvanization process, as starting material by simple heat treatment method. The as-synthesized ZnO obtained were further underwent post-anneal and post-hydrothermal treatment series. From the characterization data, it was found that highest crystallite size was obtained in sample treated with post-hydrothermal treatment at 150oC for 12 hours with value of 1371 nm, which corresponds to its lowest Eg value of 3,086 eV.